running cost report 2014 lr - dimplex€¦ · the running costs of various conventional electric...

Introduction

The purpose of this

information paper is

to provide a publicly

available document for

professionally informed

decisions regarding

the running costs of

various conventional

electric heating systems

installed in UK homes,

and their running costs.

The report has been prepared

by Dr John Counsell who is an

independent researcher with

over 20 years of experience in

the design, development and

performance assessment of

electric heating systems and

their controls. The running

costs used in the comparison

study described in this paper

have been estimated using the

UK Government’s calculation

method: Standard Assessment

Procedure 2012 (SAP). SAP is a

compulsory calculation required

to comply with Part L of the

England & Wales and Section

6 of the Scotland & Northern

Ireland building regulations.

The study uses the full SAP

calculation and the latest BRE

published revision SAP2012

(2012 Edition rev Feb2014) [1].

The fuel costs used are also from

SAP published in Table 12 [1].

SAP has expanded its

coverage of energy

use in homes since its

introduction to Part L

in 1994 to cover the

whole house energy

use including the use of

renewable energy sources.

The energy prediction

method/calculations for

Space and Domestic Hot

Water heating energy

consumption have been

calculated in SAP based

on the BRE Domestic

Energy Model (BREDEM).

In the comparison of

electric heating system

running costs in this paper,

only space heating (i.e.

excluding Domestic Hot

Water) energy running

costs are used. The type of

electric heating systems

to be compared in their

running cost performances

have been confined to

conventional types of

electric heating. These

systems are based on

resistive heating elements

and do not include more

complex electric heating

systems such as heat

pumps and underfloor

electric heating systems.

The SAP/BREDEM

modelling parameters

for the heating systems

used are given and fully

explained in the report and

the attached Appendix A.

A typical High Heat Retention Heater made by Dimplex.

4

Running cost report_Inside Pages.indd 4 27/11/2014 15:44

Running Cost

Estimation using SAP

BREDEM which is the core

estimation method for predicting

the energy consumption in

UK homes is, still to date the

only known energy prediction

method that has been extensively

calibrated across the UK with a

wide range of real occupied homes.

This calibration was carried out with accurately

monitored annual and minute-by-minute data

from real occupied homes. The data from

the monitoring contained information on;

occupancy times, house temperatures, space

heating and hot water energy use and outside

weather conditions.

This unique calibration has

established BREDEM and thus SAP

as the Government and Building

industry’s trusted de facto standard

for predicting energy use in a UK

home. The BREDEM method is a

combination of empirically derived

standard occupancy patterns in two

zones in the home; the first for the

main living area and secondly the

rest of the home.

The SAP calculation procedure in

this study uses outside weather

conditions specified monthly and also

allows the UK regional weather to be

specified if required. In this study the

SAP region used is the “UK Average”

[1] as it fairly represents the average

weather conditions for space heating

energy use calculations in the UK.

5


Home 1

The first home type used

is a 1 Bedroom, 40m2 in

with an originally designed

minimum SAP space heating

energy requirement

of 6840kWh.

Home 2

The second home used is a 2

Bedroom, 65m2

originally designed minimum

SAP space heating energy

consumption of 10610kWh.

Home 3

The third home type used is

a 3 Bedroom, 90m2

area, semi-detached home

with an originally designed

SAP minimum space heating

energy consumption

of 15910kWh.

For all three types of

property two types of

construction were assumed;

first the originally built

based on 1960s building

regulation levels of

insulation and air tightness

(Tables 1 to 3) and secondly

a refurbished level of

insulation typical of building

regulations in the 1990s

(Tables 3 to 6).

The physical parameters

used for these constructions

are described in Appendix

A and were taken from the

Energy Saving Trust’s report

“Northern Ireland: assessing

U-values of existing

housing” [2].

The BREDEM method

uses these outside weather

conditions to calculate the

monthly space heating

energy required to meet the

empirically derived standard

occupancy times and comfort

temperatures of 21°C in the

main living area and 18°C in

the rest of the rooms. The

energy use calculation is

based on the conservation

of energy principle that

requires the average internal

temperatures for the

house to be derived for the

different heating systems

whilst satisfying the required

comfort temperatures during

the standard (on average)

occupancy times.

The running costs of electric

heating systems in this paper

are calculated using energy

consumptions derived

using SAP2012 energy use

estimation methods. This

energy use is combined with

a standard electric heating

tariff and an Economy 7 tariff

with kWh use unit rates as

stated in SAP2012 Table 12

[1]. With these assumptions

the SAP2012 calculation

procedure has been used

in the comparison study

described in this paper to

predict the space heating

running costs for 3 types

of homes with two levels

of insulation.

The three types of home considered are typical of

homes where electric heating is commonly used.

6


Different Types of

Electric Heating and their

SAP performance models

Direct acting heating in SAP is defined

as an electric heating system that has a

responsiveness of 1 and perfect tracking of

room temperature. A responsiveness of 1

usually describes a heating system that can

go from zero heat output to maximum heat

output with time constant response of less

than 5 minutes.

Perfect tracking of room temperature

requires a room by room thermostat, i.e.

a thermostat fitted to each heater. The

heaters that SAP considers to be of Direct

acting type include, but are not confined

to; Panel convector heaters, radiant panel

heaters (oil or ceramic filled), fan heaters

and aluminium/oil filled radiators. In

SAP modelling all these heaters have the

same responsiveness and controllability

and there is NO variation in running cost

predictions in SAP2012 between

these systems.

In the study three types

of 100% efficient electric

heating systems have been

modelled using SAP2012,

they are as follows:

Direct Acting (Direct):

Manually Charged Storage

and Secondary Direct

Acting Heaters (Storage):

This heating system is defined

in SAP2012 and consists of

the modern high heat retention,

digitally controlled fan assisted

storage heaters with secondary

direct acting heating

(such as panel convector heaters).

High Heat Retention

Storage and Secondary

Direct Acting Heaters

(High Ret):

This heating system consists of

traditional manually charged

(i.e. no automatic charging of

the store) static storage heaters

(i.e. no fan or integrated radiant

panel heater) in the home with

secondary direct acting heaters

(such as panel convector heaters)

in, for example, bedrooms

and bathrooms.

7


Heating System Type

Electric heating system types and examples used in this SAP2012 comparative study

Direct Acting

using Standard

Rate Tariffs

[1] (Direct)

High heat retention

Storage Heaters &

Secondary Direct

Acting using E7

Tariff [1] (HHRS)

Manual Storage &

Secondary Direct

Acting Heaters

using an E7 Tariff

[1] (Storage)

8


Relative Heating

Systems’ Performances

The SAP results for the three heating systems described in Table 1 were calculated

assuming; SAP standard occupancy and thermal comfort requirements; “UK Average”

regional weather conditions and electricity tariffs described in SAP2012 Table 12 [1].

For the three case study homes as originally built these results are shown in the

following tables:

The original homes have been assumed to be

of a fabric and glazing typical of the 1960s

building standards. This was when many of

Within a reasonable budget it is feasible

to upgrade these homes with new UPVc

double glazed windows, draught proofing

and internal or external insulation to bring

homes up to insulation standards typical of

the 1990s building fabric standards.

All the key parameters for areas and

insulation for the original and refurbished

homes used in this comparative study are

given in Appendix A. The same three homes

assumed to be refurbished to the equivalent

of 1990s insulation levels according to SAP

calculations again using tariffs described in

SAP2012 [1] gave the following SAP results

in Tables 4 to 6:

Heating System Tariff Running Cost (£)

Direct Acting Convectors or Electric Radiators Standard £902

Manual Charge Storage & Convectors E7 £664

High Heat Retention storage & Convectors E7 £494

Table 1 - 40m2 1 Bed Flat as built with typical 1960s Building Regulations (refer Appendix A)





Table 2 - 65m2 2 Bed Flat as built with typical 1960s Building Regulations (refer Appendix A)





Table 3 - 90m2 3 Bed Semi-detached Home with 1960s Building Regulations (refer Appendix A)

9






Table 4 - 40m2 1 Bed Flat as refurbished with typical 1990s Building Regulations (refer Appendix A)





Table 5 - 65m2 2 Bed Flat as refurbished with typical 1990s Building Regulations (refer Appendix A)





Table 6 - 90 m2 3 Bed Semi-detached with typical 1990s Building Regulations (refer Appendix A)

In both the original and the refurbished case studies it can be observed from Tables 1 to 6

that the High Heat Retention Storage (HHRS) heating system achieves a running cost on

an Economy 7 (E7) tariff almost half that of direct acting heating on a standard tariff.

10


Potential Impact of Electric Heating

Choices on Fuel Poverty

The running costs for the three homes as they were built

(assumed to be in the 1960s) for the three heating systems as

estimated by SAP are shown in the column chart Figure 1 below:

£500.00

£0.00

£1,000.00

£1,500.00

£2,000.00

£2,500.00

1 BED FLAT 2 BED FLAT 3 BED SEMI

Direct (Standard)

Storage (E7)

HHRS (E7)

Figure 1: Annual space heating running costs (£) for all

heating systems in the three original homes

The advantage of the HHRS heating system

running costs is achieved by utilising 90%

of the electricity at the E7 off-peak rate.

SAP2012 and other price research such as

the Sutherland tables (April 2014 SE England)

which is a reputable and established source

of independent and impartial information on

domestic heating costs, state that the E7

off-peak electricity unit price to be less than

40% of the standard electricity tariff unit price.

The HHRS heating system is a revolution in

storage heating as it achieves 90% E7

off-peak electricity use without

over-heating the home which results from

poor temperature control normally associated

with older storage heating systems. Even

more modern storage convectors with manual

charging shown in this comparison study

overheat according to SAP by an average of

0.7°C. According to SAP, the results shown in

Tables 1 to 6 indicate that modern convective

storage heating systems typically use 25%

more energy than HHRS heating systems and

cost over 35% more to run in some poorly

insulated homes.

11


It is clear from both Figures 1 and 2 that the

most cost effective of the heating systems

in this study in terms of running costs is

the HHRS heating systems operating on an

Economy 7 tariff. With its vastly improved

controllability and its superior running costs

the modern HHRS heating system using

Economy 7 [1] compared with the Direct

acting system using a Standard Electricity

tariff [1] presents the best conventional

electric heating solution for homes aiming

to reduce running cost and fuel poverty.

These running costs are also predicted

by assuming that the SAP’s standard

occupancy comfort conditions are achieved

(e.g. The average expected comfort

conditions of a UK homes) and thus present

a high level of confidence that the running

costs will be achieved with thermal comfort

conditions at levels expected by all in a

modern UK society.

The relative percentage savings by

HHRS heating systems improves slightly as

a home is refurbished with better glazing,

draught proofing, building fabric and roof

insulation. There is a lot of confusion with

government bodies, architects, heating

system designers, installers and users to

why storage based heating systems can

deliver much lower running costs whilst

using more energy, improve thermal

comfort and reduce building fabric and

glazing condensation.

The energy increase especially from

modern HHRS heating systems is very

small compared with the benefit of using

90% of the heating energy required using

electricity which is less than half the price

of that of Standard Rate electricity, i.e. off-

peak electricity generally available between

midnight and 7am in the morning every day

of the week and throughout the year.

The running costs for the homes refurbished to insulation standards

typical of 1990s building regulations for the three heating systems

are shown in column chart Figure 2 below.

1 BED FLAT 2 BED FLAT 3 BED SEMI

£200.00

£400.00

£600.00

£800.00

£1,000.00

£1,200.00

£1,400.00

£0.00

Direct (Standard)

Storage (E7)

HHRS (E7)

Figure 2: Annual space heating running costs (£) for all

heating systems in the three refurbished homes

12


Author’s Biography

Dr John Counsell is the Managing Director of Advanced Control Partnerships Limited

and a BRE Trust Fellow sponsored by BRE at the University of Liverpool where he is an

active member of BRE’s and DECC’s SAP scientific integrity group. He was previously

the R&D group manager for advanced domestic electric heating for the electricity

industry at EA Technology and the holder of the BRE. Chair in Energy Utilisation at the

University of Strathclyde.

Author’s signature.

Advanced Control Partnerships Limited

54 Grange Cross Lane

Wirral

CH48 8BQ

Email: [email protected]

Any claims of significant energy saving due to more accurate digital control of room

temperatures by direct acting heating is considered negligible (i.e. less than 1 or 2%)

in the SAP2012 model.

In SAP2012 the energy waste due to poor temperature control using Direct acting

systems and HHRS heating systems is modelled as being identical, i.e. Zero!

Conclusion

In conclusion using the de facto model SAP2012 for prediction of space heating energy

consumption in UK homes, this comparison study showed that HHRS heating systems

using an E7 tariff [1] on average reduce running costs compared with Direct Acting

systems using a Standard Rate tariff [1] by between 45 and 47%.

13


House Parameter / Description Value / Units

Wall Fabric U value 0.55 W/K/m2

Roof U value 0.35 W/K/m2

Suspended sealed Floor U value 0.45 W/K/m2

Non sealed, Wooden Frame Single Glazing U value 3.1 W/K/m2

Living area fractions 1 bed = 0.5

2 bed = 0.4

3 bed = 0.3

House Parameter / Description Value / Units

Wall Fabric U value 1.7 W/K/m2

Roof U value 1.5 W/K/m2

Suspended sealed Floor U value 0.6 W/K/m2

Non sealed, Wooden Frame Single Glazing U value 4.84 W/K/m2

Living area fractions 1 bed = 0.5

2 bed = 0.4

3 bed = 0.3

Table A1 - Home SAP parameters as originally built, assumed to be in the 1960s [2]

Table A2 - Home SAP parameters as refurbished to 1990s insulation levels [2]

Heating System Type and Control SAP Parameters Value

Direct Acting using Standard Rate

Tariffs [1] (Direct)

SAP Heating Type:

SAP Responsiveness (R):

SAP Percentage from Secondary Direct-acting heaters

1

1

0%

Manual Storage & Secondary

Direct Acting Heaters using an

E7 Tariff [1] (Storage)

SAP Heating Type:



5

0.2

15%

High heat retention Storage Heaters

& Secondary Direct Acting using

E7 Tariff [1] (High Ret)

SAP Heating Type:



2

0.8

10%

Table A1 - Heaters’ SAP2012 Parameters

References

1. BRE (Published on behalf of DECC), “SAP2012, The Government’s Standard

Assessment Procedure for Energy Rating of Dwellings”, 2012 Edition,

rev February 2014.

2. Energy Savings Trust, “Energy Efficiency Best Practice in Housing, Northern

Ireland: assessing U-values of existing housing”, March 2005, CE127.

14


15


Running Costs of Conventional

Electric Space Heating Systems

Dr John Counsell

Advanced Control Partnerships Limited

A

B

CD

E

F

G


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